1. Field of the Invention
This invention relates to pumps, particularly pumps for introducing fluids into the human body, as well as syringes, bottle caps and the like for use in connection with such pumps for gallstone dissolution and the like.
2. Description of the Prior Art
Solidified masses such as biliary duct stones and gallstones may develop in hollow organs or ducts within humans and animals and cause numerous health problems, as is known to those skilled in the art. These deposits may be removed from the body in various ways, including surgery or in vivo dissolution by solvents introduced into the localized area of the body, such as the gallbladder, where the stones are located.
In order to effectively dissolve stones such as gallstones in vivo, however, an effective means of introducing and distributing the fluid is necessary; agitation of the fluid is advantageous and speeds up the dissolution process substantially; it can be accomplished by repeatedly cycling or oscillating the fluid into and out from the body area of interest. Furthermore, an effective dissolving agent is necessary; monooctanoin, for example, can be used, and methyl tertiary-butyl ether ("MTBE"), for example, has been found to be very effective, but is quite flammable. Moreover, while MTBE is non-toxic so long as it remains confined to the gallbladder, it is highly toxic if supplied in sufficient volume to cause leakage from the biliary duct into the surrounding tissues.
Any apparatus for injecting and aspirating MTBE, therefore, would advantageously include safety features designed to limit either the pressure of fluids within the body cavity or the volume of fluid injected therein and would be constructed of materials not degraded or dissolved by the solvent. In addition, to avoid fire, the pump and control system should be such that the solvent is never exposed to electrical spark.
Pumps have been designed for use in such dissolution systems. For example, in U.S. Pat. No. 4,723,941, a piston pump is disclosed for oscillating methyl tertiary-butyl ether ("MTBE") and other solvents into the gallbladder. In U.S. Pat. No. 4,655,744, another pump is disclosed which provides a fluid trap between the gallbladder and the pump to remove the bile. However, an effective flexible but simple closed system pump with minimal air leakage and with optimum handling of all functions desirable in a dissolution pump has not previously been developed.
Other pumps having multimodal operation have been designed for various applications, such as that described in U.S. Pat. No. 3,382,811, but require several displacement mechanisms and are designed to provide a constant output flow in the mainstream output line.